Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light

ABSTRACT

A method and apparatus for detection of a particular material, such as photo-resist material, on a sample surface. A narrow beam of light is projected onto the sample surface and the fluoresced and/or reflected light intensity at a particular wavelength band is measured by a light detector. The light intensity is converted to a numerical value and transmitted electronically to a logic circuit which determines the proper disposition of the sample. The logic circuit controls a sample-handling robotic device which sequentially transfers samples to and from a stage for testing and subsequent disposition. The method is particularly useful for detecting photo-resist material on the surface of a semiconductor wafer.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/842,513, filed Apr. 25, 2001, pending, which is a continuation ofapplication Ser. No. 09/475,439, filed Dec. 30, 1999, now U.S. Pat. No.6,256,094 B1, issued Jul. 3, 2001, which is a divisional of and claimspriority from application Ser. No. 08/964,451, filed Nov. 4, 1997,pending.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to the manufacture ofsemiconductor wafers prepared by a method including applying aphoto-resist layer, exposing the layer, and stripping the layer from thesemiconductor wafer. More particularly, this invention pertains to amethod for inspecting semiconductor wafers or other substrates todetermine the presence of residual photo-resist material on thesemiconductor wafer surface.

[0004] 2. State of the Art

[0005] Semiconductor chips are produced in a multi-step process by whicha plurality of identical electronic circuits is typically formed on asemiconductor substrate, such as a silicon wafer. The semiconductorsubstrate is then subdivided (diced) into individual chips which arefurther processed into semiconductor devices.

[0006] The electronic circuits are generally patterned into asemiconductor wafer by lithography. In this process, a resist materialis coated onto the semiconductor wafer surface. As disclosed in commonlyowned U.S. Pat. No. 5,350,236, issued Sep. 27, 1994, hereby incorporatedherein by reference, the application of a material on a semiconductorsubstrate can be monitored by measuring light reflected from a surfaceof the semiconductor substrate.

[0007] After the resist material has been coated on the semiconductorwafer surface, it is selectively exposed to a radiation source, such asby the passage of radiation (i.e., light, e-beam, or X-rays) through amask having the desired pattern. Some portions of the resist receive ahigh dosage of radiation while other portions receive little or noradiation, resulting in a difference in solubility from the resistportions. In a subsequent development step, a developer removes oretches portions of the resist coating from the semiconductor substrateat a rate higher than other portions. The selective removal results in aresist pattern which will become the electronic circuit pattern on thesemiconductor substrate. Precision in the development time is criticalfor achieving complete removal of resist from some portions whileleaving other portions substantially intact. Both insufficientdevelopment and excessive development will result in a lack ofdifferentiation, forming a defective electronic circuit pattern on thesemiconductor substrate. In addition, where the width of a conductorline(s) in the electronic circuit is critical, inadequate developmentresults in an overly narrow line, and excessive development produces anoverly wide line. Thus, precise endpoint detection (i.e., the moment atwhich precise development occurs) is a requirement for properdevelopment.

[0008] Following the removal of the portions of the photo-resistmaterial in the development process, the semiconductor wafer issubjected to further processing steps which may include doping, etching,and/or deposition of conductive materials in unprotected areas, i.e.,areas devoid of photo-resist material. After one or more of theseprocessing steps, the semiconductor wafer is subjected to a strippingstep to remove the photo-resist material remaining on the semiconductorwafer.

[0009] After the removal of the photo-resist material, a subsequentprocessing step may include heating the semiconductor wafer in adiffusion furnace or applying a layer of material with a chemical vapordeposition system. Occasionally, a semiconductor wafer is inadvertentlypassed to a thermal furnace or vapor deposition system without removalor with only partial removal of the photo-resist material. The resultingdamage to the processing equipment may be severe. For example, furnacediffusion tubes are irreparably damaged by vaporized hydrocarbons andcarbon from the photo-resist material and, thus, the furnace diffusiontubes must be replaced. The replacement equipment and/or the downtime torepair the processing equipment is usually very costly.

[0010] Furthermore, the photo-resist carrying semiconductor wafer andone or more subsequent semiconductor wafers entering the processingequipment prior to shutdown of the equipment are usually alsocontaminated and must be discarded. At a late stage of manufacture, asemiconductor wafer may have a value between about $10,000 and $20,000.Thus, even an occasional loss is significant.

[0011] One method used in the industry to detect such residualphoto-resist material is manual inspection with a microscope. However,manual inspection of semiconductor wafers to detect photo-resistmaterials has not been sufficiently effective. First, photo-resist istypically difficult to see using a conventional white light microscope,and even an experienced microscopist may inadvertently miss photo-resiston a wafer. Secondly, since manual inspection is laborious andtime-consuming, it is generally not cost-effective to manually inspectmore than a very small number of the semiconductor wafers (usually lessthan 10%). Thus, unstripped semiconductor wafers may still be missed bymanual inspection.

[0012] Accordingly, an object of the present invention is to provide animproved method for rapid automated detection of resist material onsemiconductor wafers in order to reduce process downtime, materialwastage, maintenance/repair expenses and production costs.

SUMMARY OF THE INVENTION

[0013] The present invention is an automated method and apparatus fordetermining the presence or absence of a photo-resist material on thesurface of a semiconductor substrate by the detection of fluorescence,reflection, or absorption of light by the photo-resist material.

[0014] Photo-resist materials are generally organic polymers, such asphenolformaldehyde, polyisoprene, poly-methyl methacrylate, poly-methylisopropenyl ketone, polybutene-1-sulfone, poly-trifuluoroethylchloroacrylate, and the like. Organic substances can generally fluoresce(luminescence that is caused by the absorption of radiation at onewavelength followed by nearly immediate re-radiation at a differentwavelength) or will absorb or reflect light. Fluorescence of thematerial at a particular wavelength, or reflection/absorption by thematerial of light at a given wavelength, may be detected and measured,provided the material differs from the underlying semiconductorsubstrate in fluorescence or reflection/absorption at a selectedwavelength or wavelengths. For example, a positive photo-resistgenerally fluoresces red or red-orange and a negative photo-resistgenerally fluoresces yellow.

[0015] In a particular application of the invention, the presence ofphoto-resist material on a semiconductor wafer surface may be rapidlyand automatically determined, recorded, and used to drive an apparatuswhich separates semiconductor wafers based on the presence or absence(or quantity) of the photo-resist material. Thus, semiconductor waferswhich have been incompletely stripped of photo-resist material (or notstripped at all) may be automatically detected and culled from amanufacture line of fully stripped semiconductor wafers and reworked.Thus, contamination of downstream processes by unstripped semiconductorwafers is avoided.

[0016] In this invention, the semiconductor wafer is irradiated withlight which may be monochromatic, multichromatic, or white. In oneversion, the intensity of generated fluorescence peculiar to thephoto-resist material at a given wavelength is measured. In anotherversion, the intensity is measured at a wavelength which is largely oressentially fully absorbed by the photo-resist material. In a furthervariation, the intensity of reflected light is measured at a particularwavelength highly reflected by the photo-resist material but absorbed bythe substrate.

[0017] The intensity of fluoresced or reflected light is measured by asensing apparatus and the result is put to a logic circuit, e.g., acomputer. The result may be recorded and used for a decision making stepand control of a robotic device. The robot performs the semiconductorwafer handling tasks, such as transferring the semiconductor wafers froma semiconductor wafer cassette to an inspection stage, and transferringthe inspected semiconductor wafers to a destination dependent upon thetest results.

[0018] A permanent record of the test results may be automaticallyretained and printed, and semiconductor wafers identified as beingpartially or totally unstripped or otherwise abnormal or defective areseparated for proper disposition.

[0019] The apparatus for conducting the detection test process isgenerally comprised of known components which in combination produceaccurate results in a very short time without laborious manualinspection. A high test rate may be achieved in a continuous orsemi-continuous manufacturing process, enabling all product units to betested. The current laborious and time-consuming testing of a few randomsamples by manual microscopic inspection methods is eliminated. The testresults are in electronic digital form and may be incorporated into acomprehensive automated manufacturing documentation/control system.

[0020] The test apparatus may comprise a stand-alone system throughwhich individual substrate units are passed for a separatedetection/measurement step. Thus, for example, following a strippingstep, semiconductor wafers may be moved sequentially through the testapparatus for confirmation of full stripping, and for culling ofnon-stripped semiconductor wafers.

[0021] In another version of the invention, the test apparatus may beincorporated into a processing step such as embodied in a resiststripping device for in situ determination of residual resist materialon semiconductor wafers undergoing stripping. The stripping end-pointmay be thus determined and may be used to activate automated transfer ofthe stripped wafers from the resist stripper to the following processstep when stripping is complete. This embodiment is particularlyadaptable to plasma and wet-stripping apparatuses.

[0022] While the method and apparatus are particularly described hereinas relating to the detection of photo-resist material in a lithographicprocess, they may also be used to detect the presence and quantity ofany material on a semiconductor substrate, where the material andsemiconductor substrate have differing fluorescing/absorbing propertiesat a given selected wavelength of radiation. The material may be anorganic substance having naturally fluorescing properties under aparticular spectrum of radiation, or may be a substance with littlenatural fluorescence, spiked with a material which fluoresces whenirradiated with light of a particular wavelength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] While the specification concludes with claims particularlypointing out and distinctly claiming that which is regarded as thepresent invention, the advantages of this invention can be more readilyascertained from the following description of the invention when read inconjunction with the accompanying drawings in which:

[0024]FIG. 1 is a diagrammatic view of an automated photo-resistmaterial detection apparatus of the invention;

[0025]FIG. 2 is a graphical representation of exemplary results ofdetection tests conducted on a series of semiconductor wafers;

[0026]FIG. 3 is a diagrammatic view of a further embodiment of theautomated photo-resist material detection apparatus of the invention;and

[0027]FIG. 4 is a diagrammatic view of an additional embodiment of theautomated photo-resist material detection apparatus of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] With reference to the drawings, and particularly to FIG. 1, oneembodiment of an automated photo-resist material detection apparatus 10of the invention is shown. The illustrated components are generally notshown to scale.

[0029] An optical portion 12 of the photo-resist material detectionapparatus 10 includes a light source 14 for generating a primary lightbeam 16 and a dichroic or dichromatic mirror 18 for directing at leastsome wavelengths of the primary light beam 16 onto a sample 20, i.e.,the semiconductor wafer, through a focusing lens 22. An excitationfilter 24, such as a band pass filter, may be positioned in the path ofprimary light beam 16 for removing wavelengths from the primary lightbeam 16 which do not stimulate fluorescence, reflect, or absorb in thesample 20.

[0030] As well known, the dichromatic mirror 18 reflects wavelengths ofless than a given value, and passes wavelengths greater than the givenvalue.

[0031] Where fluorescence of the sample 20 is desired, light source 14is preferably a high energy lamp such as a mercury or xenon lamp whichproduces high intensity fluorescence-inducing illumination.

[0032] The sample 20 is preferably mounted on a stage 26 which ismovable by motive means 28 to provide the desired positioning of thesample in the primary light beam 16. A robotic device 30 loads thesample 20 onto the stage 26 and removes it after the test to anotherlocation for further processing, or alternatively, to a location fordiscard if the undesirable material is found on the sample 20.

[0033] A secondary light beam 32 of fluoresced light and/or reflectedlight emanating from the sample 20 is shown passing through thedichromatic mirror 18 to a light intensity sensor 34, such as a silicondiode sensor. The light intensity sensor 34 sends an electronicintensity signal 36 to a power meter 38, which converts the electronicintensity signal 36 into an electronic numerical value signal 40readable by a logic circuit 42 (such as a programmable computercircuit), preferably an analog to digital conversion in the power meter38. A small desktop computer may be used as the logic circuit 42.

[0034] The sample 20 may be a substrate 44 having a layer or coating 46of a material which differs from the substrate in fluorescing,absorption, and/or reflection properties at some wavelengths of incidentlight. The sample 20 may be a semiconductor wafer comprising a slice ofcrystalline silicon (silicon wafer) or may include varioussemiconductive material or material layers, including without limitationsilicon wafers, silicon-on-insulative (SOI) structure,silicon-on-sappline (SOS) structure, gallium arsenide, or germanium uponwhich a layer of photo-resist material has been coated, processed andsubsequently stripped.

[0035] Other lenses and filters, not shown, may be used to provide thedesired light beam characteristics. As shown in FIG. 1, the secondarylight beam 32 of fluoresced and/or reflected light from the sample 20 ispassed through a suppression filter 48 to absorb non-fluoresced light orundesired reflected light and produce a filtered light beam 32Asubstantially free of such undesired wavelengths. The filtered lightbeam 32A may be further passed through a band pass filter 50 to producea band pass filtered light beam 32B having a narrow wavelength band of,for example, 700 nm+/−80 nm. Such a wavelength is a characteristicfluorescing emission of commonly used positive photo-resist materials,as listed above.

[0036] The optical portion 12 of the photo-resist material detectionapparatus 10 may comprise a microscope adapted for measurement of thefluorescent/reflected secondary light beam 32 from the sample 20.

[0037] While the photo-resist material detection apparatus 10 may beused simply to determine the presence of a photo-resist material orother material on a substrate surface, its utility is enhanced byautomation by which the samples 20 are moved to and from stage 26 byrobotic device 30 as known in the art. Disposition of each sample 20 isdetermined by the test result therefor, and instructions 52 generated bya programmed logic circuit 42 are relayed to the robotic device 30 forproper control thereof. In a preferred embodiment, the stage 26 is movedalong X-Y coordinates by instructions 54 from the logic circuit 42,enabling testing at multiple locations, preferably nine or more, on thesample 20. Because of the high rate at which the tests may be conducted,all wafers in a production line may be tested, greatly enhancing thedetection of unstripped resist material.

[0038] It is also, of course, understood that the primary light beam 16can be a sheet beam having a width approximately the width of the sample20. The sample 20 can be passed through the sheet beam which will resultin the inspection of the entire surface of the sample 20.

[0039] In one embodiment of the photo-resist material detectionapparatus 10, the power meter 38 converts the electronic intensitysignal 36 into a simple digital “0” or “1” value, depending upon whetherthe electronic intensity signal 36 is less than or more than a selectedcutoff value. This is useful when the decision is simply one ofacceptance or rejection.

[0040] In other embodiments of the photo-resist material detectionapparatus 10, the power meter 38 may produce an electronic numericalvalue signal 40 representative of (in proportion to) the measured lightintensity.

[0041] The detection surface test area of the sample 20 which providesthe fluoresced or reflected secondary light beam 32 for a test may vary,depending upon the desired resolution. Thus, for detecting the presenceof photo-resist material on a narrow slot location of a wafer, thediameter of the measurement circle may be very small, e.g., less than afraction of a mil. The measurement of light intensity from such smallareas may require prior light amplification. However, for someapplications, the measurement circle may be much larger, and lightamplification may not even be required.

[0042]FIG. 2 shows the fluoresced light intensity output from theapparatus of FIG. 1, where tests were conducted on a series oftwenty-two substrates 44 in the form of semiconductor wafers. Strippedslots were formed on all but five of the semiconductor wafers (numbers1, 5, 10, 15 and 20) which remained unstripped. Three tests wereconducted on each semiconductor wafer, the results averaged by computerand printed as a continuous line 58. Light intensities are shown inwatts, as determined by the power meter 38. The unstripped semiconductorwafers produced light intensity values of about (1.2 to 1.4)×10⁻⁰ ⁰⁸watts, while intensity values were about (1.0 to 2.0)×10⁻⁰ ⁰⁹ watts forthe stripped semiconductor wafers. As shown, an intermediate cutoffvalue 60 of light intensity may be selected as the basis foracceptance/rejection of each semiconductor wafer 56 by the roboticdevice 30.

[0043] Another version of the photo-resist material detection apparatus10 of the invention is shown in FIG. 3. A primary beam 70 of highintensity radiation is generated by a lamp 72 and directed into a filtercube 74 to be reflected onto the sample 20 through a focusing lens 76.As available commercially, filter cubes 74 comprise a plurality ofoptical light paths as exemplified by 78A, 78B, and 78C, each with adichroic mirror 80 for directing primary beam 70 optionally throughoptical filters 82 of differing characteristics, through the focusinglens 76 onto the surface 84 of the sample 20. The filter cube 74 isrotatable about a vertical axis 77 for selectively aligning a desiredoptical light path 78A-C with the high intensity lamp 72 and focusinglens 76. The dichroic mirrors 80 in the selectable optical light paths78A-C may have different reflectance properties. The fluoresced andreflected light (output light) 86 from the sample 20 passes back throughthe focusing lens 76 and selected dichroic mirror 80 of the filter cube74, and through optional optical filter 88 to an output lens 90 normallyused for observation.

[0044] As illustrated in FIG. 3, the output light 86 from the outputlens 90 of the filter cube 74 is directed into a photo-multiplier tube(PMT) 92 which sends an electronic signal 94 to a computer 96 forrecording, analysis and decision making. Signals 98 generated bycomputer 96, programmed with appropriate software, control movement ofthe stage 100. Signals 102 control robot 104 for sample movement ontothe stage 100 and for disposition of the tested sample 20 from thestage.

[0045] The use of the filter cube 74 enables a rapid trial of variouswavelengths of fluoresced/reflected light to determine the mostadvantageous output wavelength for production testing.

[0046] As shown in FIG. 4, the photo-resist material detection apparatus10 may be incorporated into a stripping tool 110 for in situ automateddetermination of the progress in stripping of material layer 46 from thesurface 112 of a semiconductor wafer 56. Elements common between FIGS.1-3 and FIG. 4 retain the same numeric designation. The strippingprocess may comprise wet- or dry-stripping performed in a strippingchamber 114. The stripping chamber 114 is illustrated herein with aplasma generator 130. The stripping chamber 114 has one or twoentryways, not shown, for the introduction and removal of thesemiconductor wafers 56 by a robot 116. The semiconductor wafer 56 isshown on a movable stage 118 within the stripping chamber 114. Themovable stage 118 may be movable by one or more stepper motors 120 orother motive means controlled by electronic signals 122 from a computer124.

[0047] Two optical ports 126, 128 are positioned in a wall 132 of thestripping chamber 114. A primary high energy beam 134 of light from lamp136 passes through a first optical port 126, strikes the surface 112 ofthe semiconductor wafer 56 and is reflected as reflected beam 138 at anangle through the second optical port 128. Fluoresced and/or reflectedlight produced by existing material layer 46 on surface 112 in responseto the primary high energy beam 134 is also present in reflected beam138. The reflected beam 138 is passed through an optical band passfilter 140 and into a photo-multiplier tube 142 for generation of anelectronic signal 144 indicative of the light intensity at the filteredlight wavelength. The electronic signal 144 is received by a softwareprogram in the computer 124 and processed to provide instructions 146 tothe robot 116 for removal of the wafer 56 from the stripping chamber114. Electronic signals 122 are also sent by computer 124 forcontrolling motion of the movable stage 118.

[0048] The primary high energy beam 134 is shown in FIG. 4 as strikingthe wafer 56 at an angle of about 45 degrees. The angle 137 betweenprimary high energy beam 134 and reflected beam 138 is preferablybetween 0 and 90 degrees. However, by using a dichromatic mirror as inFIGS. 1 and 3, primary high energy beam 134 and reflected beam 138 mayboth pass through the same optical port 126 or 128, and angle 137 is 0degrees.

[0049] The high energy lamp 136 is typically a mercury or xenon lamp,and the output may be filtered by a band pass filter 148 to provide thedesired wavelengths for producing fluorescence, reflectance, and/orabsorption in the particular resist material.

[0050] As indicated, the method depends upon a difference influorescence or light absorption/reflectance between the material to bedetected, e.g., the photo-resist and the underlying substrate. Awavelength of incident illumination is typically chosen which maximizesthe difference in fluorescence, absorption, or reflectance. It ispreferred to use fluorescence as the measured output, but lightabsorbence may be used when the material to be detected strongly absorbsa particular wavelength of radiation while the substrate stronglyreflects the same.

[0051] It should be understood that references herein to light of aparticular “wavelength” encompass wavelength bands that are “about” aparticular wavelength. In other words, the term “a particularwavelength” may include wavelengths both slightly longer and shorterthan the “particular wavelength”.

[0052] The advantages of this method over prior resist inspectionmethods are substantial.

[0053] First, the test is rapid and automated, enabling all wafers to betested. The inadvertent passage of unstripped wafers to downstreamprocess equipment, with concomitant costly contamination and destructionof the equipment, may be virtually eliminated.

[0054] Second, laborious and time-consuming visual inspections forresist are eliminated. Such tests are less than adequate, in any case.

[0055] Third, the detection method is adaptable to any type of resist orother material which may be applied to a substrate surface. This isbecause the process may be based on the quantitative differences betweenthe material and the substrate in fluoresced light, reflected light, orabsorbed light. Particular wavelengths are chosen to accentuate thesedifferences.

[0056] Fourth, the apparatus for conducting the automated resistdetection tests comprises an assembly of readily available equipmentitems.

[0057] Fifth, the software program for controlling the robot and movablestage may be very simple and easy to construct.

[0058] Sixth, the process and equipment may be readily incorporated in abatch, continuous or semi-continuous manufacturing process for accuratein situ determination of the end-point of resist stripping. Such useenhances the accuracy of end-point determination.

[0059] Seventh, the automated test method and control thereof may beincorporated in a comprehensive manufacturing documentation and controlsystem.

[0060] Eighth, the method may be used to determine the presence of amaterial in a very small area, or alternatively in a relatively largearea, by using an appropriate optical lens.

[0061] Having thus described in detail preferred embodiments of thepresent invention, it is to be understood that the invention defined bythe appended claims is not to be limited by particular details set forthin the above description, as many apparent variations thereof arepossible without departing from the spirit or scope thereof.

What is claimed is:
 1. An apparatus for in situ monitoring of strippingmaterial from a semiconductor substrate, comprising: a stripping chamberconfigured for stripping material from a semiconductor substrate; astage for positioning said semiconductor substrate within said strippingchamber; a first optical port for allowing a beam of high energy lightto enter into said stripping chamber onto a surface location of saidsubstrate; a second optical port for allowing fluoresced and/orreflected light from said surface location as a secondary light beam toexit said stripping chamber; and a light intensity sensing apparatus forreceiving said secondary light beam from said stripping chamber andmeasuring an intensity thereof.
 2. The apparatus of claim 1, furthercomprising a source for producing said beam of high energy light.
 3. Theapparatus of claim 2, wherein said source is selected from a groupcomprising a xenon lamp and a mercury lamp.
 4. The apparatus of claim 1,wherein said first optical port further comprises a band pass filtercapable of restricting the beam of light to a predetermined wavelengthband.
 5. The apparatus of claim 1, wherein said second optical portfurther comprises an optical band filter.
 6. The apparatus of claim 1,wherein said light intensity sensing apparatus is configured forgenerating an electronic signal representative of said measured lightintensity.
 7. The apparatus of claim 6, further comprising a logiccircuit for processing said electronic signal.
 8. The apparatus of claim7, further comprising an automated substrate handling apparatus formoving said substrate to and from said stage, wherein said handlingapparatus is configured to move said substrate at least partially inresponse to said signal.
 9. The apparatus of claim 7, wherein said logiccircuit comprises a computer programmed to receive and record said lightintensity measurement.
 10. The apparatus of claim 1, further comprisinga plasma generator.
 11. The apparatus of claim 1, wherein said lightintensity sensing apparatus comprises a photo-multiplier tube.
 12. Theapparatus of claim 1, wherein said stage is movable.
 13. A method fordetecting a presence of at least one material on a surface of asemiconductor substrate, comprising: providing a stripping chamber forstripping material from a semiconductor substrate, said strippingchamber comprising a first optical port for allowing light to enter saidchamber and a second optical port for allowing said light to exit saidchamber; providing a light source; directing light from said lightsource to enter said chamber through said first optical port and ontosaid surface of said semiconductor substrate; collecting light emanatingfrom said surface of said semiconductor substrate through said secondoptical port; and generating a signal indicative of an intensity of saidcollected light.
 14. The method of claim 13, further comprisingstripping material from said surface of said semiconductor substrate.15. The method of claim 13, further comprising transmitting said signalto a logic circuit for processing.
 16. The method of claim 15, whereinsaid logic circuit generates an instruction for transmission to anautomated substrate handling apparatus to control disposition of saidsubstrate based on said collected light intensity.
 17. The method ofclaim 15, wherein said logic circuit generates an instruction fortransmission to a movable stage to control disposition of saidsemiconductor substrate based on said collected light intensity.
 18. Themethod of claim 13, further comprising filtering said reflected and/oremitted light in at least one wavelength indicative of said material.19. The method of claim 13, further comprising transmitting said signalto a programmed computer for processing.
 20. The method of claim 19,further comprising: sequentially positioning additional semiconductorsubstrates to receive said light directed through said first opticalport on to said surface of each of said additional semiconductorsubstrates; and sequentially collecting light emanating from saidsurface of each of said additional semiconductor substrates.
 21. Themethod of claim 13, further comprising moving said semiconductorsubstrate into and out of said chamber using an automated substratehandling apparatus.
 22. The method of claim 12, further comprisingdetermining a presence of said at least one material by detecting aselected wavelength of light emanating from said surface of saidsemiconductor substrate, said selective wavelength of light beingcharacteristic of said at least one material.